Adjustable intervertebral implant

ABSTRACT

An adjustable intervertebral implant for implantation into a patient&#39;s spine in-between first and second adjacent or neighboring vertebrae. The implant may include one or more of the following features: (i) inner and outer members coupled by a radiographically imageable expansion ring, (ii) detachable endplates coupled to the implant via a polygonal press-fit coupling interface that accommodate a range of lordotic endplates to be applied to the implant using any surgical approach, (iii) an interference pre-loaded set screw for selectively locking the height of the construct, (iv) a radiographically imageable marker for determining the expansion of the implant, and (v) an asymmetric thread coupling between the expansion ring and the inner member.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/061,388, filed Feb. 28, 2011, entitled “ADJUSTABLE INTERVERTEBRALIMPLANT” which was a National Stage of International Application No.PCT/2008/07251, filed Sep. 4, 2008, the entire disclosures of which ishereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an intervertebral implant, and, moreparticularly, to an adjustable height intervertebral implant thatpreferably enables the user to adjust the height of the implant.

Degenerative disc disease or degeneration of a vertebral body oftenresults in a loss of disc height, which in turn can cause, inter alia,facet and nerve impingement. One standard of care is to replace thedamaged intervertebral disc with an intervertebral implant or a damagedportion or an entire vertebral body with an intervertebral implant. Thatis, after removal of a damaged intervertebral disk, a damaged nucleuspulpous of an intervertebral disk or a damaged portion or entirevertebral body, an intervertebral implant is inserted into theintervertebral space of two neighboring vertebral bodies or into thespace created by removal of portions of or the entire vertebral body.Preferably the intervertebral implant restores the spine as much aspossible to a natural state, i.e. to restore the original height of theintervertebral disk and thus the original distance between the twoneighboring or adjacent vertebral bodies or vertebral bodies in variouslevels of the spine.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to an adjustable intervertebralimplant for insertion between first and second vertebral bodies. Theimplant may include a first member, a second member, and an expansionring operatively associated with the first and second members, the ringincludes one or more threads for engaging one or more threads formed onthe outer surface of the first member so that rotation of the ringcauses the first member to axially move or translate with respect to thesecond member. The first member may be slightly smaller than the secondmember so that the first member is received at least partially withinthe second member.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofa preferred embodiment of the adjustable intervertebral implant ordevice of the present application, will be better understood when readin conjunction with the appended drawings. For the purposes ofillustrating the corpectomy implant of the present application, there isshown in the drawings a preferred embodiment of the implant and toolingfor implanting same. It should be understood, however, that theapplication is not limited to the precise arrangements andinstrumentalities shown. In the drawings:

FIG. 1 illustrates a front perspective view of an adjustableintervertebral implant in accordance with a preferred embodiment of thepresent invention;

FIG. 2 illustrates a partially exploded front perspective view of theadjustable intervertebral implant of FIG. 1;

FIG. 3 illustrates a magnified, partially exploded front perspectiveview of the adjustable intervertebral implant of FIG. 1;

FIG. 4 illustrates a cross-sectional view of the adjustableintervertebral implant of FIG. 1, taken along line 4-4 of FIG. 1;

FIG. 5 illustrates a cross-sectional view of the adjustableintervertebral implant of FIG. 1, taken along line 5-5 of FIG. 2;

FIG. 6A illustrates a top perspective view of an inner member of theadjustable intervertebral implant of FIG. 1;

FIG. 6B illustrates a rear elevational view of the inner member of FIG.6A;

FIG. 6C illustrates a cross-sectional view of the inner member of FIG.6A, taken along line 6C-6C of FIG. 6B;

FIG. 6D illustrates a cross-sectional view if the inner member of FIG.6A, taken along line 6D-6D of FIG. 6B;

FIG. 7A illustrates a top perspective view of an outer member of theadjustable intervertebral implant of FIG. 1;

FIG. 7B illustrates a side elevational view of the outer member of FIG.7A;

FIG. 7C illustrates a cross-sectional view of the outer member of FIG.7A, taken along line 7C-7C of FIG. 7A;

FIG. 8A illustrates a bottom plan view of an expansion ring member ofthe adjustable intervertebral implant of FIG. 1;

FIG. 8B illustrates a side elevational view of the expansion ring memberof FIG. 8A;

FIG. 8C illustrates a cross-sectional view of the expansion ring memberof FIG. 8A, taken along line 8C-8C of FIG. 8A;

FIG. 9 illustrates a side elevational view of a screw member of theadjustable intervertebral implant of FIG. 1;

FIG. 10 illustrates a side elevational view of a pin of the adjustableintervertebral implant of FIG. 1;

FIG. 11 illustrates a bottom perspective view of the adjustableintervertebral implant of FIG. 1 coupled to an insertion instrument inaccordance with a preferred embodiment of the present invention;

FIG. 12 illustrates a side perspective view of the adjustableintervertebral implant of FIG. 1 coupled to the insertion instrument ofFIG. 11;

FIG. 13 illustrates a magnified top perspective view of a grasping endof the insertion instrument of FIG. 11; and

FIG. 14 illustrates a partial cross-sectional view of the insertioninstrument of FIG. 11, taken along line 14-14 of FIG. 13 and showingdetails of gears of the insertion instrument.

DETAILED DESCRIPTION OF THE INVENTION

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right”, “left”, “lower” and “upper”designate directions in the drawings to which reference is made. Thewords “inwardly” and “outwardly” refer to directions toward and awayfrom, respectively, the geometric center of the adjustableintervertebral implant, the insertion tool and designated parts thereof.The words, “anterior”, “posterior”, “superior”, “inferior” and relatedwords and/or phrases designate preferred positions and orientations inthe human body to which reference is made and are not meant to belimiting. The terminology includes the above-listed words, derivativesthereof and words of similar import.

An exemplary embodiment will now be described with reference to thedrawings. In general, such embodiments relate to an intervertebralimplant, by way of non-limiting example, an adjustable intervertebralimplant for implantation into a patient's spine in-between first andsecond adjacent or neighboring vertebrae. If used as a corpectomydevice, the intervertebral implant will be able to perform single ormultiple level operations, i.e., removal of one or more than onevertebra and/or portions of vertebra. An adjustable intervertebralimplant is further disclosed in PCT International Application No.PCT/US08/56898, filed Mar. 13, 2008, entitled ADJUSTABLE INTERVERTEBRALIMPLANT, the entire contents of which are hereby incorporated byreference.

The intervertebral implant may have alternate applications and uses tothose described herein and should not be limited to the structure oruses described and illustrated herein. That is, while the intervertebralimplant will be described as and may generally be used in the spine (forexample, in the lumbar, thoracic or cervical regions), those skilled inthe art will appreciate that the intervertebral implant may also be usedin other parts of the body, and may have other applications outside ofthe medical device field.

Referring to FIGS. 1-8C, a preferred embodiment of an adjustableintervertebral implant 100 is configured for replacing at least aportion of a diseased or damaged vertebral body. The adjustableintervertebral implant 100 includes a first body member preferablycomprising an inner member 110 having a generally tubular configuration,a second body member preferably comprising an outer member 115 having agenerally tubular configuration, and an expansion ring 130, each ofwhich are hollow so as to provide an axial bore interior to and along alongitudinal axis 101 of the adjustable intervertebral implant 100. Thatis, in use, the first or inner member 110 is preferably sized andconfigured to be slightly smaller than the second or outer member 115 sothat the first member 110 is moveably disposed within the second member115. As such, the first member 110 is generally characterized as theinner member 110 while the second member 115 is generally characterizedas the outer member 115. However it should be noted that otherarrangements of moveably associating the first member 110 and the secondmember 115 are contemplated.

As best shown in FIGS. 7A-7C, the outer member 115 preferably is asubstantially hollow, tubular member having a first end 202, a secondend 204, an outer surface 206 and an internal bore 208 extendingsubstantially from the first end 202 to the second end 204. The outermember 115 preferably includes one or more relatively large bone packingopenings 210 formed in the outer surface 206 thereof for providingaccess to the internal bore 208 such that a surgeon is able to insertbone chips or alternate graft material into the implant 100 for reasonsthat would be apparent to one having ordinary skill in the art. Theouter member 115 also preferably includes several smaller openings 212for permitting bone in-growth in the implanted configuration to promotefusion of adjacent vertebra 50, between which the adjustableintervertebral implant 100 is mounted in an implanted position. Theintervertebral implant 100 is not limited to inclusion of the bonepacking opening 210 or the smaller openings 212 and may not includeopenings 210, 212 therein or may include additional variably shapedopenings, depending upon the specific application or configuration ofthe implant 100.

As best shown in FIGS. 6A-6D, the inner member 110 preferably is asubstantially hollow, tubular member having a first end 182, a secondend 184, an outer surface 186 and a hollow interior cavity 188. Theouter surface 186 of the inner member 110 preferably includes a thread190 formed thereon. As shown, the outer surface 186 of the inner member110 preferably does not circumscribe three hundred sixty degrees (360°)so that the inner member 110 is preferably in the form a partial tubularmember. Thus the inner member 110 preferably includes a slot 192extending from the second end 184 thereof for reasons that will bedescribed below. However it should be noted that the inner and outermembers 110, 115 are not limited to having a tubular shape and may bealternatively shaped, such as square, elliptical or nearly any othershape that permits translation between the inner and outer members 110,115.

Referring to FIGS. 6A-8C, the expansion ring 130 includes an inner bore132 within which the inner member 110 is received. The expansion ring130 is also preferably moveably coupled, more preferably rotatablyattached, to the outer member 115. The expansion ring 130 may beconnected to the outer member 115 by any means that enables theexpansion ring 130 to be moveably coupled, preferably rotatablyattached, to the outer member 115 including, but not limited to asnap-fit connection, a press-fit connection, a pin and groovearrangement, etc. Preferably, the inner and outer diameters of theexpansion ring 130 and the outer member 115 are preferably similar suchthat the expansion ring 130 rests atop the outer member 115 and isretained with respect thereto via a tab 216. The tab 216 extendsupwardly from the outer member 115 and terminates in a lip protrudingsubstantially perpendicular to the longitudinal axis 101 of the outermember 115 such that the expansion ring 130 is slidably movable on andguided in its movement by the bottom of the tab 216 and the top of theouter member 115. The expansion ring 130 is allowed to rotate freelywith respect to the outer member 115 in a released position. The innermember 110 is preferably disposed interior to the outer member 115 andis aligned with respect thereto via the slot 192 that runs parallel tothe longitudinal axis 101. The slot 192 is configured to mate with thetab 216.

The interior circumference of the expansion ring 130 includes threading133 that is configured to mate with the threading 190 formed on theouter surface 186 of the inner member 110 such that rotation of theexpansion ring 130 causes the inner member 110 to translate or generallylinearly move with respect to the outer member 115 along thelongitudinal axis 101 of the adjustable intervertebral implant 100. Thatis, in use, the inner and outer members 110, 115 are preferablycoaxially disposed along a common longitudinal axis 101 and arepreferably slidably disposed (e.g., telescopic) with respect to oneanother so that the axial position of the inner member 110 is adjustablewith respect to the outer member 115. Rotation of the expansion ring 130drives a telescoping coupling between the inner and outer members 110,115 such that, rotation of the expansion ring 130 causes the inner andouter members 110, 115 to expand or contract depending on the relativedirection of the rotation.

The expansion ring 130 further preferably includes a series of teeth 134located circumferentially around its exterior surface for engagementwith a corresponding tool so that rotation of the tool, which may beeither hand operated or powered, results in rotation of the expansionring 130. In this manner, the series of teeth 134 help facilitaterotation of the expansion ring 130. Preferably, the series of teeth 134are sized and configured to engage an insertion instrument 300, whichwill be described in greater detail below. When the teeth 134 are drivenby the instrument 300, the expansion ring 130 is rotated resulting inthe inner and outer members 110, 115 moving with respect to one another.Alternatively and/or in addition, the expansion ring 130 may be rotatedmanually without the aid of the teeth 134 and insertion instrument 300,or by any other means now or hereafter known.

The intervertebral implant 100 may be constructed from any biocompatiblematerial or combination of any biocompatible material known in the artincluding, but not limited to, stainless steel, titanium, titaniumalloys, ceramics, polymers including, but not limited topolytetrafluoroethylene (“PTFE”), etc. Preferably, the inner and outertubular members 110, 115 are formed from a radiolucent material, suchas, for example, a polymer or polyetheretherketone (“PEEK”), while theexpansion ring 130 is preferably formed from a metal, such as, forexample, titanium or stainless steel. The threaded engagement betweenthe interior surface of the preferably metallic expansion ring 130 andthe exterior surface of the preferably polymeric or other radiolucentmaterial inner member 110 is characterized by a threading that has anasymmetric geometry, as best shown in FIG. 4. That is, because thethreads 133 formed on the expansion ring 130 are preferably made frommetal they are typically stronger than the threads 190 made on the outersurface 186 of the inner member 110, which are preferably made from apolymeric material. Thus, the threads 133 made on the inner surface ofthe expansion ring 130 can be made thinner than the threads 190 made onthe outer surface 186 of the inner member 110. Preferably, the metallicthreads 133 formed on the expansion ring 130 are configured so that thestrength of the metallic threads 133 is substantially similar to thestrength of the thicker polymeric threads 190 formed on the outersurface 186 of the inner member 115. More specifically, preferably, awidth W_(e) of thread crests 133 a that are formed on the interiorsurface of the metallic expansion ring 130 is thinner than a width W_(i)of thread crests 190 a that are formed the external surface of thepolymer inner member 110. The mating of the thicker polymer threads 190with the thinner metallic threads 133 provides a configuration in whichmore thread loading occurs over a shorter span of thread engagement whencompared to standard symmetrical thread forms between atypicalmaterials, in which the stronger material threads are as thick as theweaker material threads and which results in an increased area ofthreaded contact necessary to provide similar load bearing capabilities.

As best shown in FIGS. 1-3, the inner member 110 may include a superiorendplate 120, preferably, detachably coupled to the first end 182 of theinner member 110. Similarly, in the preferred embodiment, an inferiorendplate 125 is detachably coupled to the second end 204 of the outermember 115. The superior and inferior end plates 120, 125 are sized andconfigured for contacting the neighboring vertebral endplates ofneighboring vertebrae 50 and are preferably provided in a range ofsurface geometries to accommodate a range of lordotic or kyphotic anglesdisplayed by the endplates of the neighboring vertebrae 50.

The endplates 120, 125 may be connected to the inner and outer members110, 115 by any means known in the art, including, but not limited to,interference-fit, threading, screwing, bonding, etc. In this manner, theintervertebral implant 100 can be provided in a kit with a plurality ofdifferent endplates 120, 125, thus enabling the user to select thedesired endplates 120, 125 that best conform with the contours of thepatient's vertebral endplates. By way of example, various endplates 120,125 may be provided that include varying shapes including, but notlimited to, circular, square, rectangular, oval, kidney-shaped, etc.and/or one or more of the following characteristics: a generallywedge-shaped surface, curved surface, flat surface, etc. Alternatively,the upper and lower endplates 120, 125 may be integrally formed with theinner and outer members 110, 115.

Preferably, the superior and inferior end plates 120, 125 are initiallycoupled to the inner and outer members 110, 115 via a press fitcoupling, as is best shown in FIG. 2. The press fit coupling preferablyassumes the form of a polygonal interface, illustrated as an octagonalinterface, although a range of permissible geometries is envisioned,such that the desired lordotic/kyphotic taper(s) chosen for the superiorand inferior endplates 120, 125 can be quickly and removably coupled tothe adjustable intervertebral implant 100, regardless of surgicalapproach (e.g., lateral, posterolateral, anterior, posterior, etc.). Forinstance, an octagonal coupling interface enables the chosen superiorand inferior endplates 120, 125 to be coupled to the adjustableintervertebral implant 100 in forty-five degree (45°) increments withrespect to the longitudinal axis 101 such that any desired approach tothe spine is permitted. Once the desired lordotic angles of the superiorand inferior endplates 120, 125 are chosen and the endplates 120, 125are press fit to the inner and outer members 110, 115, the endplates120, 125 are secured to the inner and outer members 110, 115 usingoptional endplate caps 150, 155, which preferably, threadingly engage amating thread 151, 156, respectively, internal to the inner and outermembers 110, 115.

The surfaces of the superior and inferior endplates 120, 125 include, ina preferred embodiment, anti-expulsion features 127 such as teeth,spikes, ridges, or other surface texturing.

Referring to FIGS. 4, 5 and 8A-9, one or more preloaded set screws 160is preferably provided to selectively lock the height of the adjustableintervertebral implant 100. Each set screw 160 preferably includes athreaded shaft 162 and a head 164 having a diameter larger than that ofthe threaded shaft 162. In the preferred embodiment, a plurality,preferably five, set screws 160 a-160 e are disposed within throughslots170 a-170 e that are incrementally spaced around the external surface ofthe expansion ring 130. The throughslots 170 a-170 e thereby definingthroughslot angles centered on the longitudinal axis 101, thethroughslot angles being approximately seventy-two degrees (72°). Thethroughslots 170, as best shown in FIG. 8A, are characterized by havinga proximal portion 172 for housing the head 164 of the set screw 160 anda distal portion 174 for housing the shaft 162 of the set screw 160. Thediameter of the proximal portion 172 is preferably larger than thediameter of the distal portion 174. The diameter of the proximal portion172 of the throughslot 170 is preferably slightly smaller than thediameter that characterizes the head 164 of the set screw 160. Due tothe geometry of the throughslots 170, preferably two points of contactexist between the head 164 of the set screw 160 and the proximal portion172 of the throughslot 170, such that the set screw 160 is retainedwithin the throughslot 170 regardless of whether the set screw 160 hasbeen tighten. As such, the head 164 of each set screw 160 resistsrotation and translation of the set screw 160 during implant loading,vibration, shipping and handling, or other sources not introduced by theappropriate instrument, e.g., a screwdriver, thereby enabling the setscrews 160 to be preloaded into the expansion ring 130.

In a preferred embodiment, the adjustable intervertebral implant 100 isprovided with the plurality of set screws 160 preloaded or alreadysecured within the plurality of through slots 170 at a depth sufficientto enable the expansion ring 130 to be freely rotated and provide adesired construct height while still insuring the secure coupling of theset screws 160 within the throughslots 170 due to the interferencetherebetween. The advancement of any one of the set screws 160 via anappropriate instrument causes the distal end 165 of the rotationallyadvanced set screw 160 to bear against the outer surface 186 of theinner member 110 and prevent the expansion ring 130 from furtherrotation, thereby locking the height of the adjustable intervertebralimplant 100. Preferably, in use, a surgeon needs only advance any oneconveniently accessible set screw 160 to lock the position of theexpansion ring 130 and thus the height of the adjustable intervertebralimplant 100. The secure coupling of the preloaded set screws 160 to theexpansion ring 130, which is provided by the interference between thehead 164 of the set screws 160 and the proximal portion 172 of thethroughslots 170, enables the set screws 160 to be preassembled into theexpansion ring 130 and securely retained therein, thereby eliminatingthe extra step of inserting one or more set screws 160 in an appropriateone of the throughslots 170 during surgery and avoiding potential lossof the relatively small set screws 160.

While the interference between the head 164 of the set screw 160 and theproximal portion 172 of the throughslot 170 has been described as beingcharacterized by two points of contact therebetween, it is envisionedthat a similar degree of interference can be provided by a range ofdifferent interference geometries, such as one or more points ofcontact, or entire or partial surface area contact between the head 164of the set screw 160 and the proximal portion 172 of the throughslot170. Due to the strength of coupling between the head 164 of the setscrew 160 and the proximal portion 172 of the throughslot 170 providedby the interference therebetween, it is envisioned that otherapplications may gain benefit from similarly preloaded set screws underinterference, such as transconnectors serving as “ladder rungs” betweenparallel-implanted spinal rods, wherein the set screw includes a beveleddistal end that bears against a spinal rod and urges the spinal rodlaterally into a rod-retaining receiving portion of the transconnector,such that the extra step of inserting the relatively small set screwinto the transconnector is eliminated and the likelihood of surgicalcomplications (e.g., losing or dropping the tiny set screw) is reduced.

Referring to FIGS. 1-4, 6C, 6D and 10, the adjustable intervertebralimplant 100 preferably also incorporates a pin 180. The pin 180 ispreferably disposed within a bore 194 formed in the inner member 110near the second end 184 of the inner member 110. The pin 180 ispreferably constructed of a dense radiographically imageable materialsuch as Titanium-Aluminum-Niobium (TAN). In a preferred embodiment, asbest shown in FIGS. 6D and 10, the pin 180 is an elongated cylinder thatis disposed generally perpendicular to the longitudinal axis 101 of theinner member 110 so as to be parallel to the radial axis of theexpansion ring 130 such that, when the adjustable intervertebral implant100 is implanted and viewed radiographically, a surgeon can gauge howmuch expansion has taken place and how much expansion is still affordedby the adjustable intervertebral implant 100 by viewing the longitudinalaxis of the pin 180 with respect to the parallel disposedradiographically visible image of the expansion ring 130. When theadjustable intervertebral implant 100 is fully expanded, the pin 180 ispreferably positioned close to or may be occluded by the expansion ring130.

Referring to FIGS. 11-14, an expansion and insertion instrument 300 isprovided for use with the adjustable intervertebral implant 100. Theexpansion and insertion instrument 300 includes a handle 310, a shaft330 and a translatable sleeve 335 disposed around the shaft 330. Thesleeve 335 further includes a distally tapered end 338. Disposed alongthe proximal portion of the shaft 330 are a first manipulating mechanism320 and a second manipulating mechanism 325. Disposed near the distalend of the shaft 330 is a pair of grasping claws 350 and a gear 340.Actuation, preferably rotation, of the first manipulation mechanism 320causes one or both of the grasping claws 350 to open and/or close toenable the grasping claws 350 to surround the outer member 115 or torelease the outer member 115. In the preferred embodiment, as best shownin FIG. 13, rotation of the first manipulating mechanism 320 forces thesleeve 335 to translate distally along the shaft 330 and causes thedistal taper 338 to engage the interior surface 352 of the proximalportion 351 of the grasping claws 350, thereby pivoting the graspingclaws 350 closed about a pivot point provided by a pin that secures thegrasping claws 350 to the expansion and insertion instrument 300. Thatis, in use, initially, the grasping claws 350 are opened so that thegrasping claws 350 can surround the outer member 115. The firstmanipulating mechanism 320 is then actuated, e.g., rotated, to translatethe sleeve 335 distally along the shaft 330 to thereby engage the matingsurfaces of the interior of the proximal end of the grasping claws 350and the distal taper 338 of the sleeve 335, thereby causing the interiorsurface of the grasping claws 350 to firmly grasp the outer member 115.

In the preferred embodiment, the outer member 115 includes one or moreinstrument engagement features, which may be in the form of indentationsor grooves, that mate with the interior surface of the distal end 354 ofthe grasping claws 350 or alternative surface features thereupon. Whenthe adjustable intervertebral implant 100 is securely coupled to theexpansion and insertion instrument 300 via the grasping claws 350, thegear 340 functionally contacts the series of teeth 134 formed on theouter surface of the expansion ring 130. Actuation, preferably rotation,of the second manipulating mechanism 325 causes the gear 340 to rotateand, in turn, causes the expansion ring 130 to rotate with respect tothe adjustable intervertebral implant 100, which in turn causestelescopic expansion or contraction of the adjustable intervertebralimplant 100, depending on the direction of rotation.

In operation, the adjustable intervertebral implant 100 may optionallybe filled by the surgeon with bone graft material within its axial boreto allow fusion between the neighboring vertebral endplates of theneighboring vertebrae 50 and through the adjustable intervertebralimplant 100. A surgeon elects the desired lordotic taper for thesuperior and inferior endplates 120, 125 and press fits the superior andinferior endplates 120, 125 to the inner and outer members 110, 115,respectively, at any one of several positions, depending on the electedsurgical access path provided by the polygonal interface therebetween.The surgeon then preferably chooses to secure the endplates 120, 125 tothe adjustable intervertebral implant 100 using the superior andinferior endplate caps 150, 155. The adjustable intervertebral implant100 is engaged with the insertion and expansion instrument 300 using thegrasping claws 350 via the actuation of the first manipulation mechanism320. The adjustable intervertebral implant 100 is preferably implantedin its lowest height configuration between the neighboring vertebralendplates of the neighboring vertebrae 50 and expands the adjustableintervertebral implant 100 in situ using the second manipulationmechanism 325 while visualizing radiographically the height expansion ofthe adjustable intervertebral implant 100, taking into account theposition of the image of the pin 180 and the image of the expansion ring130. Once the desired height of the adjustable intervertebral implant100 is reached, one of the set screws 160 is advanced using a simpleinstrument, such as a screwdriver, to lock the height of the adjustableintervertebral implant 100.

While the foregoing description and drawings represent the preferredembodiment of the present invention, it will be understood that variousadditions, modifications, combinations and/or substitutions may be madetherein without departing from the spirit and scope of the invention asdefined in the accompanying claims. In particular, it will be apparentto those skilled in the art that the invention may be embodied in otherspecific forms, structures, arrangements, proportions, and with otherelements, materials, and components, without departing from the spiritor essential characteristics thereof. One skilled in the art willappreciate that the invention may be used with many modifications ofstructure, arrangement, proportions, materials, and components, whichare particularly adapted to specific environments and operativerequirements without departing from the principles of the invention. Inaddition, features described herein may be used singularly or incombination with other features. The presently disclosed embodimentsare, therefore, to be considered in all respects as illustrative and notrestrictive, the scope of the invention being indicated by the appendedclaims, and not limited to the foregoing description.

I claim:
 1. An adjustable intervertebral implant for implanting betweenadjacent vertebrae bodies to replace all or a significant portion of adamaged vertebra, the adjustable intervertebral implant comprising: aradiolucent inner member having a longitudinal axis extending between afirst end and a second end, an outer surface, a throughslot extendingfrom the second end along the longitudinal axis, a first threading onthe outer surface, and a coupling interface at the first end; aradiolucent outer member having a longitudinal axis extending between afirst end and a second end, an internal surface, an outer surface, a tabprotruding from the first end along the longitudinal axis andterminating in a lip protruding substantially perpendicular to thelongitudinal axis of the outer member, the inner member slidablyreceived within the outer member and being slidably movable along thelongitudinal axis, the slidable movement guided by interaction of thetab protruding from the outer member with the throughslot formed in theinner member, the outer member including a coupling interface at thesecond end; a radiographically visible expansion ring having inner andouter surfaces, the inner surface having a second threading thereon,wherein the width of crests of the first threading is greater than awidth of the crests of the second threading, the expansion ring receivedaround the tab protruding from the outer member and below the lip so asto be freely rotatable with respect to the outer member, actuation ofthe expansion ring results in engagement of the first and secondthreading and slidable translation of the inner member with respect tothe outer member, the expansion ring further including a plurality ofunthreaded throughslots disposed circumferentially around the expansionring, the throughslots characterized by a proximal portion and a distalportion, wherein the proximal portion is characterized by a diameterlarger than a diameter of the distal portion; and a plurality ofpre-loaded set screws having a head and a threaded shaft, the head ofthe set screw positioned within the proximal portion of the throughslotby an interference fit, wherein advancement of any one of the set screwswithin a corresponding throughslot causes the distal end of the setscrew to bear against the outer surface of the inner member and therebysecure the inner member relative to the outer member in a lockedposition.
 2. The adjustable intervertebral implant of claim 1, furthercomprising: detachable superior and inferior endplates having couplinginterfaces for attachment to the coupling interfaces of the first end ofthe inner member and the second end of the outer member, respectively.3. The adjustable intervertebral implant of claim 2, wherein thecoupling interfaces are comprised of a polygonal coupling interfaceallowing the endplate to be coupled to the inner or outer members at anynumber of positions that correspond to the number of sides of thepolygon.
 4. The adjustable intervertebral implant of claim 2, wherein atleast one of the superior or inferior endplates includes a lordotic orkyphotic taper.
 5. The adjustable intervertebral implant of claim 1,further comprising: a radiographically imageable marker disposed withinthe inner member.
 6. The adjustable intervertebral implant of claim 5,wherein the radiographically imageable marker is comprised of a pinmounted proximate the second end of the inner member.
 7. The adjustableintervertebral implant of claim 6, wherein the pin includes a pin axis,the pin axis oriented generally perpendicular to the longitudinal axisof the inner member.
 8. The adjustable intervertebral implant of claim1, wherein the distal end of at least one of the plurality of pre-loadedset screws engages a planar apex of the first threading of the innermember in the locked position.
 9. The adjustable intervertebral implantof claim 1 wherein the second end of the inner member is positionedproximate the second end of the outer member and the first end of theinner member is positioned proximate the first end of the outer memberin a loading position, the second end of the inner member positionedproximate the first end of the outer member in a fully expandedposition.
 10. The adjustable intervertebral implant of claim 9 furthercomprising: a radiographically imageable pin mounted proximate thesecond end of the inner member.
 11. The adjustable intervertebralimplant of claim 1 wherein the plurality of pre-loaded set screws iscomprised of five (5) pre-loaded set screws.
 12. The adjustableintervertebral implant of claim 11 wherein the throughslots are evenlyspaced circumferentially around the expansion ring, thereby definingthroughslot angles centered on the longitudinal axis, the through slotangles being approximately seventy-two degrees (72°).
 13. The adjustableintervertebral implant of claim 1 wherein the outer member includes aninstrument engagement feature.
 14. The adjustable intervertebral implantof claim 1, wherein the coupling interfaces of the first end of theinner member and the second end of the outer member have anoctagonal-shape.
 15. An adjustable intervertebral implant for implantingbetween adjacent vertebrae bodies to replace all or a significantportion of a damaged vertebra, the adjustable intervertebral implantcomprising: an inner member having a longitudinal axis extending betweena first end and a second end, an outer surface, a throughslot extendingfrom the second end along the longitudinal axis, a first threading onthe outer surface; an outer member having a longitudinal axis extendingbetween a first end and a second end, an internal surface, an outersurface, a tab protruding from the first end along the longitudinal axisand terminating in a lip protruding substantially perpendicular to thelongitudinal axis of the outer member, the inner member slidablyreceived within the outer member and being slidably movable along thelongitudinal axis, the slidable movement guided by interaction of thetab protruding from the outer member with the throughslot formed in theinner member; an expansion ring having inner and outer surfaces, theinner surface having a second threading thereon, the expansion ringreceived around the tab protruding from the outer member and below thelip so as to be freely rotatable with respect to the outer member,rotation of the expansion ring resulting in engagement of the first andsecond threading and translation of the inner member with respect to theouter member, the expansion ring further including a plurality ofunthreaded throughslots disposed circumferentially around the expansionring; and at least one set screw having a head and a threaded shaft,wherein advancement of the set screw within a corresponding throughslotcauses the distal end of the set screw to bear against the outer surfaceof the inner member and thereby secure the inner member relative to theouter member in a locked position.
 16. An adjustable intervertebralimplant for implanting between neighboring vertebral bodies to replaceall or a significant portion of a damaged vertebra, the adjustableintervertebral implant comprising: a radiolucent inner member having alongitudinal axis extending between a first end and a second end, anouter surface, a throughslot extending from the second end along thelongitudinal axis, a first threading on the outer surface; a radiolucentouter member having a longitudinal axis extending between a first endand a second end, an outer surface, the inner member slidably receivedwithin the outer member and being slidably movable along thelongitudinal axis; a radiographically visible expansion ring havinginner and outer surfaces, the inner surface having a second threadingthereon, wherein a width of crests of the first threading is greaterthan a width of the crests of the second threading, the expansion ringbeing rotatably coupled to the outer member so that rotation of theexpansion ring results in engagement of the first and second threadingand slidable translation of the inner member with respect to the outermember, the expansion ring further including a plurality of unthreadedthroughslots disposed circumferentially around the expansion ring; atleast one set screw wherein advancement of the set screw within acorresponding throughslot causes a distal end of the set screw to bearagainst the outer surface of the inner member and thereby secure theinner member relative to the outer member in a locked position.